Corrosion-resistant austenitic steel not requiring nickel



United States CORROSION-RESISTANT AUSTENITIC STEEL NOT REQUHIING NICKEL Dennis J. Carney, Chicago, 111., assignor to United States Steel Corporation, a corporation of New Jersey No Drawing. Application November 19, 1953,

Serial No. 393,219

zclaims. 01. 15-126 This invention relates to a corrosion-resistant, austenitic steel containing substantial amounts of' chromium and manganese but little or no nickel.

The scarcity of nickel has led to many attempts in recent years to develop a substitute for all orpart of it in conventional nickel-bearing stainless steels. The most desirable steel developed as a result of such, attempts has substantially the following percentage composition:

Such steel, however, does not have as high a resistance to corrosion as desirable and exhibits poor forging and rolling qualities. Its austenite phase is unstable and the presense of nitrogen in excess of .20%, furthermore, leads.

to the production of unsound ingots manifesting excessive bleeding. A higher chromium content is desirable to increase corrosion resistance but causes an increase in ferrite as well as too numerous rejections for rolling defects.

I have invented an iron-chromium-manganese alloy which exhibits improved corrosion resistance and good rolling and forging qualities, as well as greater stability of austenite and desirable physical properties. In general, my alloy contains more chromium and considerably more nitrogen than known steels of the same type, and is relatively free of ferrite at high temperatures. In particular, the nitrogen should be at least .25 and may be as high as 1.0%. At a manganese level of 14 to 20%, the ratio of nitrogen to chromium, furthermore, should be from .015 to .035. This is contrary to the experience with steel of the analysis given above but, even with such increased amounts of nitrogen, the ingots are sound and free from porosity. Apparently the increased chromium plus manganese permits a higher nitrogen content without causing the bleeding of the ingots and the increased nitrogen dispenses with the need for any added nickel. There will usually be present, of course, a small or residual percentage of nickel, i. e., .2% or less.

-:calcium cyanamide. The steel has better corrosion resist- I 2 The preferred ranges of percentage composition of my improved steel are:

( .05-.15 Mn 1.4-17 Si .251.0 P .01.05 s .01--.0s Cr- 17 --18.5 Ni .05 1!) N .251.0 C 0-1.0 e Balance A preferred example has the percentage composition:

C .10 Mn 16 Si .4 v P .05

S .05 Cr 17.5 Ni .10 N .35 Cu Residual Fe Balance Such steel may be made byconventional practice. The

nitrogen may be supplied by addition to the liquid steel of, for example, ferro-chromium containing-nitrogen, or

mice and austenite stability (being relatively free of ferrite at high temperatures) than the chromium-manganesenickel steel mentioned above, and also good physical properties. Italso is easier to forge and roll at high temperatures. Ingots thereof are sound and non-porous. A nitrogen content of at least .25 is necessary along with at least 17% chromium and, 14% manganese, to produce these results. More than 1% nitrogen is undesirable and more than 18.5% chromium or 17% manganese is unnecessary. The following table gives the composition of several further-examples designated by heat numbers:

TABLE I Chemical composition 0 Mn P S Si Ni Cr N Patented .Jan. 22, 1957 Thefollowing table gives the percentage of ferrite existing in the above examples when heated to different temperatures for various times:

I claim: 1. Alloy steel'consisting of "from .06 to .15 carbon, from 14 to 20% manganese, from 17 to 18.5% chromium,

TABLE II M zero-structure As Percent Ferrite After Indicated Time at Temperatures Hear Number Forged, percent 1,900 F. 2,100 F. 2,200 F. 2,300 F.

56 45 min., Trace. 5-6 45 min., 78%.

5 45 min., None. 7-8 45 111111., 10%. 6:7 90 min, 78%. 6 45 min., 56%. 4-5 min., 545%. 6 90 min., 7-8%. 56 90 mi.n., 10 5-6 90 min., 243%... 90 min.,.5-6%.- None 90 min., None..- 1 min he. None min, None..- do 90 min;-,.No'ne;

. 90min., 1%... 00min, Trace.- 00 min, 1% 7-8 90 min., 78% 90 min., 34% 90 min.,.10.%.

The physical properties of the improved steel compare favorably with those of A. I. S. I. Types 301 and.302,i except: that the percent elongation is lower after. cold; rolling, Such properties are given in the following .table :1

from .05.to.1.00% ,.nickel,.from .25 to 1.0% silicon, from .25 to-1.'0%'- nitrogen-.,.and.thebalance iron except for residual impurities usually present in such steel, the ratio of nitrogen to chromium heing betweemOlS and .035, said TABLE III" Heat Number Condition Hardness, Gauge Yield Ultimate Percent Rockwell Strength Strength Elongat1on-- Hobrolled, Annealed; B94. 1174 63, 100 50. 0 Cold-rolled C30. 0 1086- 101; 000, 32.0 Cold-rolled C36. 5 .0962. 130, 400 19.0

G0ld-r0l1ed-30%; (140.0 .0845 154, 4001 9.0 I Hot-rolled, Anne 1394.5 .1250; 64, 550 50.10. 43 Gold-rolled 10%. C32. 5 .1090 114,150 29.0 C0ld-r0lled-20% C37; 5 1003' 139, 700 1500 C rolled C41. 0 .0860, 10.0 lotgrollleda Annealed... $2, 328 3%..3 0 r0 e .1, 9 Type 301 Cold-rolled 20%... 126, 550 2630 Cold-rolled 30 133, 600 23.0 e2 2 0 -r0 e 7 ';-0 Type 502 Cold-rolled 20%... 105, 700 22.0 Oold-ro1ed-30'7f 125, 600 145, 350 13. 0

The corrosion resistance of -myimproved 'steel' is but slightly less than that-of A: I. I. Types'30-1 and-302" erties and the facts that no nickel needbeiadded and,

that the ingots are sound and free fromaporosity.

Although I 1 have disclosed... herein the. preferred ,em: bodiment of my improved steel, I intend to cover as well any changes or modifications made therein which may be made without departing from the spirit and scope of the invention.

steel exhibiting good corrosion resistance, good rolling and forging qualities and being highly austenitic.

2. Alloy steel .comprisingabout .10% carbon, about 16% manganese, about 17.5% chromium, about .4% silicon, about .35 %"nitrogenand 'the'ba-lance ironexcept for residual impurities usually present in such'" steel," the ratio ofnitrogen to chromium being 'about".02,' said'jsteel exhibiting goodleorrosionresistance, good rolling and forginggualities and beinghighlyaustenitic.

References .Gited'inthefile, of this patent:

FOREIGN PATENTS 152,29l- Austria Jan. 25, 1938 

1. ALLOY STEEL CONSISTING OF FROM .06 TO .15% CARBON, FROM 14 TO 20% MANGANESE, FROM 17 TO 18.5% CHROMIUM, FROM .05 TO 1.00% NICKEL, FROM .25 TO 1.0% SILICON, FROM .25 TO 1.0% NITROGEN AND THE BALANCE IRON EXCEPT FOR RESIUDAL IMPURITIES USUALLY PRESENT IN SUCH STEEL, THE RATIO OF NITROGEN TO CHROMIUM BEING BETWEEN .015 AND .035, SAID STEEL EXHIBITING GOOD CORROSION RESISTANCE, GOOD ROLLING AND FORGING QUALITIES AND BEING HIGHLY AUSTENITIC. 